下列电器工作过程中，把电能转化为机械能的是：[ ]
A．电磁继电器
B．发电机
C．电饭煲
D．电动机
答案：D
He can’t______ what has happened to the wheat, for it was very dried this winter.
A．look out
B．figure out
C．work out
D．take out
柴油机燃烧室有几种类型？各有何结构特点？
